The present invention relates to the control of the feed mechanism for hot or warm rolling mills of the pilger variety, for rolling a hollow bloom in sections, under utilization of a process sometimes called Mannesmann process or reciprocating rolling.
The feed mechanism in such rolling mills are usually constructed to operate on the basis of thermodynamics in the general sense. For example, pneumatically operated piston drives and liquid brakes are used here. These fluid type devices pose, of course, the usual problems of sealing, cavitation, maintenance and wear. But not only that, they have additional, operative limitations. For example, the mandrel rod of the feed mechanism must be moved against steadily increasing compressive pressure. Another limitation is the rather short period of time needed to adequately accelerate the masses to be moved. Thus, the compression of operation fluid is the higher the faster one has to operate the feed mechanism. Construction and maintenance are correspondingly high for these devices.
Certain more or less spontaneous and unexpected changes in the control of these known feed mechanisms are unavoidable because it is, for example, very difficult to synchronize advance and retraction in the feed mechanism with the rotation of the rolls. It may occur that the front point of reversal of the feed mechanism is exceeded. The resulting strong load on the rolls and drive spindles may lead to fractures. Progress in the field of pneumatics and hydraulics have not remedied these problems.